When Ga or Al atoms are supplied on a clean GaAs surface under As-free or low As pressure atomosphere, they are quite mobile and migrate very rapidly on the growing surface. This characteristic was utilized for growing atomically-flat GaAs-AlGaAs heter-interfaces, and for lowering the growth temperature. The method is based on metal-organic chemical vaper deposition and employs alternate supply of gaseous sources. (AlAs)n(GaAs) superlattices and AlGaAs-GaAs single quantum wells were grown using this method, and characterized with X-ray diffraction, photoluminescence, and Raman scattering measurement. These measurements revealed improved flatness of AlGaAs-GaAs heterojunction interfaces grown by this method.